This invention relates to an apron table arrangement for a drafting unit, comprising a guiding table which carries at least one bottom apron and which is provided with a table top which can be swivelled away from a bottom delivery roller.
From the German Patent Document DE-AS 23 10 105, an apron table arrangement of the above-mentioned type is known which is provided with a table top which can be swivelled away from the bottom delivery roller. By means of the swivel arrangement of the table top, it is to be achieved that in the case of a lap formation at the bottom delivery roller, damage to the apron table or to the bottom apron and running disturbances are avoided. These occur particularly when a bottom apron arranged close to the bottom delivery roller comes in contact with a lap formed at the bottom delivery roller. In the above-mentioned patent document, it is suggested that the table top is disposed in a socket of a bottom apron bridge in a swivelling manner by means of a projection formed in the area of this boundary edge. A leaf spring which is arranged on the underside of the table top reaches over a longitudinal shoulder of the bottom apron bridge in the manner of a clamp. When a lap is formed at the bottom delivery roller, this lap presses against the bottom apron and thus swivels the table top, which is arranged in a swivelling manner, and the bottom apron guided over it gradually away from the bottom delivery roller. By the force of this leaf spring, the table top which may be swivelled away, is held in an engagement with the bottom apron bridge during its swivel movement. The known arrangement has the particular disadvantage that the swivelling table top during its swivel movement is not guided sufficiently securely. Furthermore, the provided leaf spring requires increased constructional expenditures. Finally, fiber fly can easily catch in the area of the leaf spring.
It is an object of the invention to provide an arrangement of an apron table by means of which the secure guiding of the table top is ensured during its swivel movement.
In order to achieve this object, it is suggested according to the invention that the table top has a projection which is provided on both sides with respective opposite surfaces which are guided during the swivel movement of the table top in a positively locking manner in a receiving device constructed as a connecting link guide.
By means of the development according to the invention, it is achieved that the table top is guided precisely and securely during its swivel movement because of the positively locking guiding of the projection in the receiving device. A detaching or an undesirable shifting of the table top during the swivel movement is excluded as a result of the positively locking guiding. Furthermore, the arrangement according to the invention has the advantage that the table top of the apron able which carries the deflecting edge is swivelled away precisely corresponding to the thickness of the lap at the bottom delivery roller. Thus, the swivelling angle of the table top that can be swivelled away is a function of the respective thickness of the lap forming at the bottom delivery roller.
In a development of the invention, it is suggested that the opposite surfaces and the connecting link guide are configured in such a manner that a moving of the table top out of the receiving device is possible only after a swivelling of the table top. As a result, it is ensured that when a lap formation occurs on the bottom delivery roller, the table top that can be swivelled away is first held securely in the receiving device. Only after a swivelling of the projection about a predetermined angle, will it be easily possible to pull the projection with the table top connected with it out of the receiving device, and thus lift off the whole apron table arrangement. Subsequently, cleaning work can be carried out in an unhindered manner on the bottom delivery roller. The installation of the apron table takes place in the reverse manner in that the projection is introduced again into the corresponding receiving device.
In the case of a further development of the invention, the receiving device has curved guiding surfaces in its end area which are arranged opposite and at a distance from one another and which have a common center of curvature. Thus, this area of the receiving device is constructed with cylindrical surfaces which are arranged at a distance from one another and which have a common center of curvature. During the swivel movement of the table top, the corresponding opposite surfaces of the projection are guided on these guiding surfaces of the receiving device. Thus, the projection is moved along a curvature following the curved path of the guiding surfaces. This has the result that the table top does not carry out a linear movement but a swivel movement as long as the projection is moved along the curved guiding surfaces. So that the table top is swivelled away from the bottom delivery roller, the center of curvature of the guiding surfaces, which at the same time is also the swivelling point of the projection, must be arranged on the side of the projection which faces away from the bottom delivery roller. In order to permit the desired guiding within the guiding surfaces, the opposite surfaces of the projection must be adapted to the contour of the corresponding guiding surfaces. The projection therefore has opposite surfaces which rest against the guiding surfaces of the receiving device. Advantageously, the guiding surfaces are bounded on one side by a stop surface and on the other side by surface lines. At the surface lines, the guiding surface facing the bottom delivery roller changes into a plane guiding surface and the guiding surface facing away from the bottom delivery roller changes into a curved guiding surface. Thus the guiding surfaces on the side which faces the underside of the table top end in surface lines where one of the guiding surfaces leaves the radius of curvature. At this point, both guiding surfaces lose their guiding function for the projection, even though the curvature is continued at the supporting surface facing away from the bottom delivery roller. The guiding surfaces of the receiving devices may be constructed in a very short length. They may possibly be reduced almost to the surface lines themselves.
In an advantageous further development of the invention, it is provided that the course of the stop surface, of the guiding surfaces and of the supporting surface is constructed approximately in the shape of an S.
It is advantageous for the receiving device to be arranged in a holding device which is provided with an essentially horizontally extending supporting surface on which the table top rests with its underside in its operating position. This horizontally extending supporting surface secures the apron table additionally against a movement in the direction of the bottom delivery roller. It also supports the apron table against the pressure forces which act from the weighting arm onto the apron table.
In a further development of the invention, it is provided that the opposite surfaces of the projection are adapted to the corresponding guiding surfaces of the receiving device in such a manner that, in the operating position of the apron table, a front face of the projection rests against the stop surface of the receiving device. So that the apron table and the apron winding around it do not rest on the bottom delivery roller in the operating position, the swivel movement of the apron table in the direction of the bottom delivery roller must be limited. This is achieved by means of the stop surface provided in the receiving device on which the front face of the projection rests in the operating position. In this case, a type of construction is advantageous in which the front face of the projection is completely enclosed by the connection between the two guiding surfaces of the receiving device.
In a further development of the invention, it is provided that the guiding surfaces of the receiving device extend along the whole circumferential length of the opposite surfaces of the projection. As a result, a particularly good and uniform guiding is achieved during the swivel movement of the table top. It is a function of the length of the opposite surfaces which swivel angle results during the swivel movement. For the length of the swivel movement, the central angle which is formed by the circumferential lengths of the opposite surfaces of the projection is decisive, which central angle is specifically measured from the surface lines of the receiving device in the direction of the end of the projection. The opposite surfaces end where the radius of curvature is left. If the opposite surfaces, dimensioned according to the center angle formed by them, have different lengths, the swivel angle is determined by the smallest center angle which is formed by one of the two opposite surfaces. As soon as, during a swivel movement, that point of an opposite surface at which it leaves the radius of curvature exceeds the above-mentioned surface line of the assigned guiding surfaces of the receiving device, both opposite surfaces will no longer rest against the two guiding surfaces of the receiving device. As a rule, the stop can then, possibly after a transverse movement, be pulled out of the receiving device. Advantageously, the center angle of one of the opposite surfaces of the projection formed by the circumferential length is smaller than that of the other opposite surface. As mentioned above, the length of the swivel movement is a function of the shortest of the two opposite surfaces relative to the center angle formed by them. If the apron table is to be produced for a very specific swivelling angle, it is sufficient, when machining the stop, to take into account only one, specifically the shorter of the two opposite surfaces. Since the other opposite surface does not have to be taken in account with respect to its length, the manufacturing expenditures are reduced.
In an advantageous further development of the invention, it is provided that the center of curvature is situated between connecting lines which extend from the center of the bottom apron roller to the deflecting edge of the table top in the operating condition and in the swivelled-up condition. In the operating condition, the connecting line will then be situated between the deflecting edge and the center of the bottom apron roller below the center of curvature. The bottom apron is made of a material which has a certain elasticity and permits a linear expansion. During the operating condition, the bottom apron is tensioned in itself because of its elasticity. As a result of the fact that the swivel point of the projection during the operating condition is situated above the connecting line between the deflecting edge and the center of the bottom apron roller, the apron table is held in its operating position because of the tension of the apron.
Advantageously, the projection can be constructed in one piece with the table top and can be molded onto it. This reduces manufacturing expenditures. In addition to the lower manufacturing expenditures, the further advantage is achieved that unnecessary edges at which fiber fly may collect are avoided. Expediently, the table top and the projection may be made of plastic. It is possible to produce the profile for the table top and the projection in a length of several meters and then cut the table top with the projection in each case in the required length off this longitudinal profile made of plastic. Since, in contrast to the known constructions, additional components, such as leaf springs and screws, are not required, the manufacturing of such an apron table is particularly simple. Naturally, instead of the plastic material, another material may be advantageously used by means of which the manufacturing of the profile is possible in a simple and cost-efficient manner.
It is advantageous, during the operating condition, for an element of the weighting arm to rest with spring pressure against the table top. It is known that during the operating condition the top aprons rest against the bottom aprons, the top aprons being spring elastically disposed in the weighting arm. If the apron table extends in the longitudinal direction of the machine along several drafting units, for example, along the two drafting units of a twin drafting unit, it may be provided that a cage support of the weighting arm presses directly against the apron table between two drafting units.
In a further development of the invention, it is provided that a common table top is provided for several drafting units arranged next to one another in the longitudinal direction of the machine. Since, in the case of such a development of the invention, a separate table top and separately provided holding elements are not provided for each individual spinning unit, the manufacturing expenditures are reduced.
In a further development of the invention, it is provided that at least two holding devices are provided for one table top which are arranged at a distance from one another and which are each equipped with receiving devices for the projections of the table top. It is advantageous in this case for a holding device to be provided at least at each front face of the table top extending along several drafting units. In this case, it is particularly expedient for the spacing of the table tops to correspond to the spacing of the drafting unit system in the longitudinal direction of the machine. Conventionally, two adjacent drafting units respectively are manufactured as so-called twin drafting units, a weighting arm being provided for one twin drafting unit which receives the top rollers for both drafting units of the twin drafting unit. It is therefore particularly expedient for one table top to be provided for each twin drafting unit for the two drafting units belonging to the twin drafting units.
It is advantageous for the holding devices to have an approximately U-shaped design, the receiving devices for the projection being developed on at least one of the legs. In this case, it may advantageously be provided that the respective outer legs reach around the edge faces of the table top, and the inner legs are constructed with receiving devices having guiding surfaces. By the reaching around the edge faces of the table tops, it is achieved that a shifting of the table top, which otherwise is held only by the guiding surfaces of the receiving devices, is prevented in the longitudinal direction. Additional fastening elements for the table top are not required.
It is advantageous for the holding devices to be detachably fastened on a bearing rail extending along several spinning stations. Conventionally, it was customary to arrange the apron tables along a length between two roller stands and to fasten them to the roller stands, for example, screw them on. In the case of a lap formation on one of the bottom delivery rollers between the roller stands, for the elimination of the fault, all drafting units had to be stopped between two roller stands, so that the apron table could be removed and the disturbance could be eliminated. In the case of the further development suggested here, the table top is no longer, as customary, fastened to the roller stands, but on holding devices which, in turn, are fastened on a bearing rail. This bearing rail extends between two roller stands and is advantageously fastened to the bearing carriages for the bottom apron roller. This arrangement permits the arranging of several table tops between two roller stands which are each assigned to individual or to a small group of drafting units, particularly in each case to one twin drafting unit and are each guided in holding devices which, in turn, are detachably fastened on the bearing rail.
In a further development of the invention, it is provided that the holding devices, on the sides facing the bearing rail, have lappings which partially reach around the bearing rail while forming a form closure.